1. Field of the Invention
The present invention relates to the detection of gobs of molten glass entering molds in glassware forming machines.
2. Description of the Prior Art
In a glassware forming machine known as an IS or individual section machine, each individual section includes a plurality of means for performing a predetermined sequence of steps in a timed relationship to form the glassware. The forming means generally have been powered by pneumatic motors controlled by a valve block which, in turn, is controlled by a rotating timing drum. Glass is melted and formed into gobs which are guided to the individual sections by a gob distributor. Each section of the machine produces glassware from the gobs which glassware is placed on a dead plate for push out onto a flight conveyor. The conveyor removes the glassware to a lehr for annealing and cooling and any other treatment.
The individual sections are operated in a predetermined sequence at a relative phase difference to receive gobs from the gob distributor in ordered sequence. As one of the sections is receiving a gob from the gob distributor, another one of the sections is delivering a finished article of glassware to the conveyor and the other sections are performing various ones of the forming steps. Furthermore, two molds can be provided in each section whereby a gob is received in a first mold, called a blank or parison mold, for the initial process of forming a parison, followed by transfer of the parison to a second mold, called a blow mold, for final blowing of the article. Since each mold can have more than one cavity, each section of the machine is operating simultaneously upon a plurality of gobs to form the glassware articles.
Whether the timing drum or an electronic control system is utilized to define the timing of the sections, the prior art has synchronized the section timing with the timing of the gob feeder and the gob distributor. Not only were the sections operated at relative phase differences to receive the gobs in ordered sequence, but the phase differences had to be pre-adjusted for differences in the travel time of the gobs to the individual sections which are typically located in a line along the conveyor wherein no more than two sections might be the same given distance from the gob feeder.